Changing Seasons Can Impact A Person’s Cholesterol Levels

People with borderline high cholesterol could be at greater risk of having a heart attack during the winter months, according to a new study which reveals that both HDL and LDL levels fluctuate from season to season.

A team of researchers led by Filipe Moura, MD, a PhD student at the State University of Campinas in Brazil, evaluated lipid profiles of more than 225,000 individuals who had health screenings at primary care facilities in Campinas from 2008 through 2010. Their findings will be presented this weekend during the American College of Cardiology’s 62nd Annual Scientific Session.

They discovered that low density lipoprotein (LDL) — the so-called “bad” cholesterol — increased by an average of seven milligrams per deciliter during the winter months when compared to summer months. That increase is enough to result in an eight percent overall increase in the prevalence of high cholesterol during the winter.

“People should be aware that their cholesterol and triglyceride levels vary significantly year-round, which in some cases, may lead to a misinterpretation of a person’s actual cardiovascular risk,” Dr. Moura explained Thursday in a statement.

“This should especially concern those who are near the upper cholesterol limit as they may be at higher risk than expected. This is not to say these patients should have check-ups all the time, but we do have to keep a close eye on them and know seasonal variation may play a role,” he added.

This research reveals that high cholesterol, a known cardiovascular risk factor, could increase during the winter, like heart attacks and heart-related deaths. According to Dr. Moura, the LDL increase was more pronounced in middle-aged people and females, though that could be due to the fact that there was a larger sample size in those groups.

Furthermore, the study revealed that there were higher levels of high density lipoprotein (HDL) — the “good” cholesterol — and triglycerides — blood lipids which help enable the transfer of adipose fat and blood glucose from the liver — during the summer months. HDL levels increased by nine percent and triglyceride levels went up by five percent in the summertime, contradicting the results of previous, smaller-scale scientific studies.

The reasons for the varying cholesterol levels are partially due to environmental factors and to changes in human behavior that come with the various seasons. For example, winter months tend to lead people to consume more calories and exercise less. Additionally, shorter days of winter lead to less exposure to the sun and less vitamin D concentrations, which has been demonstrated to help the HDL and LDL cholesterol ratios.

“The change in climate and behavior that follows each season can have an effect on lipid metabolism and possibly even heart health. However, in order to make this link more research is needed,” Dr. Moura explained. Next, he and his colleagues plan to analyze patients who already suffer from cardiovascular disease, and will evaluate patients who have had heart attacks to see if there was a seasonal impact on their lipid profiles at the time.